Validation and fine mapping of a QTL for ovulation rate on swine chromosome 3

Ovulation rate (OR) is an important component of litter size, but mutation(s) in gene(s) underlying OR QTL have yet to be identified in pigs. Markers within an OR QTL on SSC3 were genotyped in three white composite lines selected for ten generations for increased OR or uterine capacity (UC), with one line being an unselected control. Numbers of corpora lutea (CL) and UC (number of fully formed fetuses) were collected at approximately 105 days of gestation, as well as ovary weight (OW), uterine length (UL) and uterine weight (UW) measurements at 160 d of age in generation 12 and 13 females from all three lines. Six microsatellites and ten single nucleotide polymorphisms (SNPs; 0-42 cM) were genotyped in pigs from all lines of generations 11 through 13. The allele frequencies of 24269.1, SW2429, 7907.2 and 7637.2 were different (P < 0.01) in the OR line compared to the control line. A significant (P < 0.05) association of CL with 24269.1 (additive effect 0.65 ± 0.32) was detected, and additive genotypic effects approached significance for markers at 28 through 35 cM (16963.2, 27514.1 and SWR1637). Haplotyping of 7637.2 and 16963.2 (31 through 32 cM) identified a significant additive association of haplotype 1 with CL (-0.62 ± 0.30). These markers were also associated with OW (24296.1 and SWR1637), UL (16963.2, 27514.1 and haplotypes of 7637.2/16963.2) and UW (haplotypes of 7637.2/16963.2). This study verifies an OR QTL on SSC3. However, based on the data, it was concluded that there may be two genes, at 13 through 18 cM and 28 through 35 cM, controlling OR on SSC3p.

148 PIGLET GROWTH AND BLOOD COMPONENTS DURING LACTATION FOLLOWING RECIPROCAL EMBRYO TRANSFER BETWEEN MEISHAN AND WHITE CROSSBRED GILTS

Sow productivity has a significant economic impact on the swine industry and is influenced by several factors, including preweaning piglet mortality. In Western breeds, low birth weight piglets exhibit the greatest susceptibility to preweaning mortality. In contrast, Meishan (MS) piglets have decreased birth weights but lower preweaning mortality rates, suggesting that birth weight is not the sole component of preweaning survival. The objective of the current study was to determine the contributions of the maternal and piglet breed and their interactions on piglet growth and blood components pertaining to survivability during lactation following reciprocal embryo transfer between MS and White crossbred (WC) gilts. Twenty-five successful pregnancies were produced by embryo transfer in 2 farrowing seasons that represented all maternal and piglet breed combinations; MS × MS (n = 4 litters), MS × WC (n = 7 litters), WC × MS (n = 7 litters), and WC × WC (n = 7 litters). At Day 1, 10, and weaning (average weaning age = 18 days), piglets (n = 147, 97, and 94, respectively at Day 1, 10, and weaning) were weighed and blood samples were taken. Hematocrit, hemoglobin, glucose, nitrogen, nonesterified fatty acids, albumin, and cortisol were measured in all blood samples. All data were analysed for ANOVA using mixed model procedures. Piglet weights were greater (P < 0.001) throughout lactation in piglets from WC dams regardless of piglet breed. As a result, average daily gains from Days 1 to 10 and weaning were greater (P < 0.05) in piglets from WC dams. There were significant (P < 0.001) maternal × piglet × day interactions for hematocrit and hemoglobin levels in which levels were greatest at Day 1 in MS piglets from WC dams and at Day 10 in MS piglets from MS dams but decreased in WC piglets from WC dams at Day 1. Glucose was greater (P < 0.05) at Day 1 in piglets from WC dams regardless of piglet breed but was greater (P < 0.05) at weaning in WC piglets regardless of maternal breed. Nitrogen was similar at Day 1 for all maternal and piglet breed combinations, but at Day 10 and weaning, nitrogen levels were greater (P < 0.001) in MS piglets regardless of maternal breed. Nonesterified fatty acid was greater throughout lactation in piglets from MS dams irrespective of piglet breed. Albumin was greater (P < 0.05) in MS piglets throughout lactation regardless of maternal breed. Cortisol was not different between the maternal and piglet breed combinations throughout lactation, but cortisol was greater (P < 0.001) at Day 1 compared with Day 10 and weaning. This study demonstrated that piglet growth during lactation was influenced more by maternal breed in favor of WC dams, which supports previous crossbreeding studies. However, blood components pertaining to survivability displayed complex interactions between the piglet and maternal breed, which may signify possible mechanisms for improved preweaning survivability of MS pigs.

Number of fetuses and conceptus growth throughout gestation in lines of pigs selected for ovulation rate or uterine capacity

Selection for 11 generations in swine for ovulation rate (OR) or uterine capacity (UC) resulted in 19.6% greater prenatal survival at term in UC compared with OR. Our objective was to characterize the number of fetuses throughout gestation in each line, including an unselected control (CO) line. Five hundred ninety-three gilts produced over 4 farrowing seasons were subjected to unilateral-hysterectomy-ovariectomy at 160 d of age and mated within line at 280 d of age. Gilts were assigned within sire family to be slaughtered (+/- 2 d) at d 25, 45, 65, 85, or 105 of gestation. Ovulation rate and number of live and dead fetuses were recorded for each pregnant gilt (n = 402). Fetal and placental weights were also recorded. Ovulation rate of OR line gilts (18.0 +/- 0.3 ova) exceeded (P < 0.001) CO and UC lines (15.0 +/- 0.3 and 14.0 +/- 0.3 ova, respectively). Line and gestational age interacted to affect number of live fetuses (P < 0.001). Least squares means for CO were 10.1, 8.3, 7.2, 6.7, and 7.3 live fetuses for d 25, 45, 65, 85, and 105, respectively (average SE = 0.46 fetuses). Corresponding means for OR were 13.4, 8.3, 7.9, 6.5, and 6.7 live fetuses, respectively (average SE = 0.44 fetuses). Means for UC were 10.2, 9.0, 8.5, 7.5, and 8.0 live fetuses, respectively (average SE = 0.47 fetuses). In each line, number of live fetuses at d 25 was approximately 72% of ovulation rate. Mortality to d 45 was greatest in OR, intermediate in CO, and least in UC. Reductions in live fetuses continued to occur from d 45 to 105, but line differences at d 45 were essentially maintained to d 105. Number of live fetuses in gilts at d 114 was estimated from each of the survival curves and predicted values of 7.0, 5.9, and 7.8 per uterine horn for CO, OR, and UC lines, respectively. Selection for uterine capacity improved fetal survival primarily during the time period between d 25 and 45. Relative growth rate coefficients throughout gestation for placental tissue indicated a change in rank of the line means, implicating a relative later growth pattern of placental tissue in the UC line.

Comparison of meat composition from offspring of cloned and conventionally produced boars

This study compares the meat composition of the offspring from boars produced by somatic cell nuclear transfer (n=4) to that of the offspring from conventionally produced boars (n=3). In total, 89 commercial gilts were artificially inseminated and 61 progressed to term and farrowed. All of the resulting piglets were housed and raised identically under standard commercial settings and slaughtered upon reaching market weight. Loin samples were taken from each slaughtered animal and shipped offsite for meat composition analysis. In total, loin samples from 404 animals (242 from offspring of clones and 162 from controls) were analyzed for 58 different parameters generating 14,036 and 9396 data points from offspring of clones and the controls, respectively. Values for controls were used to establish a range for each parameter. Ten percent was then added to the maximum and subtracted from the minimum of the control range, and all results within this range were considered clinically irrelevant. Of the 14,036 data points from the offspring of clones, only three points were found outside the clinically irrelevant range, two of which were within the range established by the USDA National Nutrient Database for Standard Reference, Release 18, 2005; website: (www.nal.usda.gov/fnic/foodcomp/search/). The only outlier was the presence of Eicosadienoic acid (C20:2) in one sample which is typically present in minute quantities in pork; no reference data were found regarding this fatty acid in the USDA National Nutrient Database. In conclusion, these data indicated that meat from the offspring of clones was not chemically different than meat from controls and therefore supported the case for the safety of meat from the offspring of clones.

A Comparison of Reproductive Characteristics of Boars Generated by Somatic Cell Nuclear Transfer to Highly Related Conventionally Produced Boars

This study compares the reproductive performance of boars produced by somatic cell nuclear transfer versus conventional breeding. Two different genotypes were selected for comparison: terminal cross line 1 (TX1) and terminal cross line 2 (TX2). The boars selected for comparison from TX1 were three cloned boars, produced by somatic cell nuclear transfer and the conventionally produced progenitor of the clones. The boars selected for comparison from TX2 were a cloned boar produced by somatic cell nuclear transfer and two conventionally produced half sibling boars that were offspring of the progenitor of the clone. Semen from each boar was collected, extended, evaluated and shipped offsite. Upon arrival, the semen was reevaluated and utilized for artificial insemination of 89 commercial gilts, at least 12 gilts per boar, producing 625 piglets. Pregnancy rates were determined at day 30 and 110 of gestation; and farrowing rate and gestation length were recorded. Differences were observed in some of the semen characteristics analyzed with the clones usually possessing superior semen quality to the control, this likely being a result of age differences amongst the clones and controls. Additionally no differences were noted between the clones and controls (progenitor) or between individual boars within genetic line for pregnancy rates, gestation length or any of the litter parameters examined between the clones and controls. These data further support previous reports with limited numbers that the reproductive capabilities of cloned boars are equal to that of conventionally produced boars.

Lack of effect of metyrapone and exogenous cortisol on early porcine conceptus development

A study was conducted to evaluate the influence of maternal cortisol on early conceptus development in pigs (Sus scrofa). The corticosteroid synthesis inhibitor metyrapone was injected daily during days 14-19 of pregnancy, without (n = 6) and with commensurate administration of cortisol (n = 6). Blood samples were taken via an indwelling jugular catheter on days 14 and 18, and conceptuses were harvested during surgery on day 20. Compared with vehicle-injected control dams (n = 7) plasma cortisol and aldosterone concentrations were decreased (P < 0.01) by 52 and 29%, respectively, by metyrapone treatment. Cortisol administration reversed decreases in plasma cortisol by day 18. There were no treatment-associated effects on conceptus survival or size. Nor were there treatment-associated effects on allantoic fluid volume or content. Trophodermal glucocorticoid receptor (GR) mRNA expression decreased by 34% (P < 0.05) in metyrapone-treated pigs, and was not further influenced by concomitant administration of cortisol, thereby suggesting an influence of aldosterone on GR mRNA expression. Also, when all pigs were considered, there were treatment-independent second-order polynomial regressions (P < 0.05) between maternal plasma cortisol concentrations and embryonic weight, allantoic size and allantoic glucose concentrations, and between plasma aldosterone concentrations and trophodermal GR mRNA expression. Such biphasic corticosteroid concentration versus tissue parameter curves are noteworthy, but difficult to interpret validly. They may suggest that an appropriate corticosteroid environment is necessary for optimal porcine embryonic development during this stage of gestation, but cannot overshadow the absence of treatment effects on the porcine embryonic measures evaluated.

Allelic variation in the secreted folate binding protein gene is associated with uterine capacity in swine1

Previous comparisons between the cDNA and gene sequences for secreted folate binding protein (sFBP) indicated a 12-bp insertion/deletion (ins/del) polymorphism in exon 1 and a SNP that altered (Ser-Arg) the protein AA sequence. The effect of the Ser-Arg SNP on reproductive traits was examined in three groups of Meishan-White European breed crossbred gilts. The gilts for all three groups were unilaterally hysterectomized-ovariectomized (UHO) at 100 d of age. Group 1 gilts (n = 77) were mated at estrus, slaughtered at d 105 of pregnancy, and a blood sample was collected from each fetus to determine fetal hematocrit. The number of corpora lutea and fetuses and the fetal and placental weights were recorded. Group 2 gilts (n = 46) were mated, the remaining uterine horn was flushed with 20 mL of saline on d 11 of pregnancy, conceptuses were counted, and flushings were measured for total sFBP. Gilts were allowed an estrous cycle to recover, mated again at estrus, slaughtered at 105 d of gestation, and the data as described for Group 1 were collected. Groups 1 and 2 gilts were genotyped for the Ser-Arg SNP. In Group 3, gilts (n = 70) and boars (n = 30) were genotyped for the Ser-Arg SNP before mating, and like genotypes were mated. Gilts were then treated as described for Group 2. The effect of the 12-bp ins/del on reproductive traits was examined in 407 white crossbred UHO gilts from a randomly selected control line and from lines selected for ovulation rate (OR) and uterine capacity (UC). Gilts were mated and slaughtered at 105 d of age, and the numbers of corpora lutea and live fetuses, and fetal and placental weights and fetal hematocrits were recorded. The 12-bp ins/del also was evaluated in 131 intact gilts from the OR selected line. These gilts were mated at approximately 250 d of age and farrowed. The numbers of fully formed and live piglets were recorded. A significant effect (P < 0.05) of the Ser-Arg SNP was detected on the number of embryos present on d 11 of pregnancy and on UC. The sFBP 12-bp ins/del was associated with UC (P < 0.01) and the number of CL (P < 0.05) in UHO gilts, but not with litter size in intact gilts from the OR line. Results suggest that the 12-bp ins/del polymorphism could be exploited to increase litter size in swine, provided that the negative effect of the polymorphism on OR is overcome.

Allelic variation in the erythropoietin receptor gene is associated with uterine capacity and litter size in swine

A single nucleotide polymorphism (SNP; C vs. T) that creates an extra GATA-1 site (T allele) in intron 4 of the swine erythropoietin receptor (EPOR) gene was discovered and a genotyping assay for this SNP was developed. A total of 402 gilts from lines selected either at random (control), for ovulation rate (OR) or for uterine capacity (UC) for 11 generations were unilaterally hysterectomized-ovariectomized (UHO) at 160 days of age, mated at approximately 250 days of age and slaughtered at 105 days of pregnancy. Blood samples and spleens were collected from each foetus and the numbers of corpora lutea (CL) and live foetuses, the weights of each foetus and placenta, and each foetal haematocrit were recorded. In addition, intact gilts from the OR line or from a Yorkshire, Landrace, Duroc, crossbred line (BX) were mated and farrowed. At farrowing, the numbers of fully formed and live piglets were recorded for each litter. Genomic DNA was isolated for both the UHO and intact gilts, from foetuses from the UHO gilts that were heterozygous for the EPOR SNP, and from the boars from the BX line and were then used to determine EPOR SNP genotypes. Only CC and CT gilts were observed in the control, OR and UC selected lines. Presence of the EPOR T allele was associated (P < 0.05) with increased UC in these gilts. The number of heterozygous and homozygous foetuses did not differ within UHO litters, or did EPOR genotype influence foetal haematocrit. In intact gilts from the OR line, litter size was significantly associated (P < 0.05) with EPOR SNP genotype. Finally, results from intact gilts of the BX line, in which both the gilt and the boar genotypes were known, allowed an analysis to determine the effect of the gilt and/or the foetal genotype on litter size. This analysis indicated that the predicted foetal genotype (with gilt genotype as covariate) was associated with litter size (an increase of 2.6 +/- 1.0 piglets born alive predicted for homozygous T litters compared with homozygous C litters, P < 0.01) whereas the effect of the gilt genotype (adjusted for foetal genotype) on litter size was not significant. These results indicate that the EPOR SNP is associated with UC and litter size in two distinct populations and could be useful in increasing litter size in swine that are not limited in OR.

Molecular cloning and endometrial expression of porcine high density lipoprotein receptor SR-BI during the estrous cycle and early pregnancy

During rapid development of the fetus, levels of high density lipoprotein (HDL) are elevated in pregnant women. The receptor for HDL, scavenger receptor class B type I (SR-BI), mediates selective cholesteryl ester uptake and is highly expressed in the human placenta. Because of the rapid growth of uterus during early pregnancy and differences in placentation between swine and humans, we hypothesized that SR-BI may be expressed in porcine endometrium to take up HDL cholesterol. The objectives of this study were to obtain the full coding region for porcine SR-BI, determine endometrial expression of SR-BI mRNA during the estrous cycle and early pregnancy, and map the gene. By iterative screening of a porcine expressed sequence tag library, we obtained the full coding region of SR-BI. Endometrial expression of SR-BI in White composite gilts (n = 3-4 each) was determined by Northern blotting on Days 10, 13, and 15 cyclic gilts and Days 10, 13, 15, 20, 30, and 40 pregnant gilts. In cyclic gilts, endometrial expression of SR-BI did not change between Days 10 and 13, but increased (P < 0.01) between Days 13 and 15. In pregnant gilts, endometrial expression of SR-BI increased (P < 0.01) between Days 10 and 13, remained elevated until Day 30, and decreased (P = 0.015) on Day 40. The SR-BI gene was mapped to 46.3 cM on chromosome 14. These results show that endometrial expression of SR-BI changes during the estrous cycle and early pregnancy, and suggest that SR-BI takes up HDL for endometrial development during early pregnancy.

Analysis of Transcriptional Control Elements in the 5′-upstream Region of Ovine Interferon-τ Gene Using Feeder-independent Caprine Trophoblast Cell Line, HTS-1

Interferon-tau (IFNtau) is a protein secreted from the embryonic trophectoderm of ruminant ungulates during peri-implantation period. This protein acts on the uterine endometrium, which indirectly maintains corpus luteum function, and is therefore considered essential for the process of maternal recognition of pregnancy. Transcriptional regulation of IFNtau genes had been examined using human choriocarcinoma cell lines, JEG-3 or JAR, however, molecular mechanisms by which cell and term specific IFNtau expression are regulated have not been elucidated. Recently, a feeder cell free-trophoblast cell line derived from Shiba-goat placenta, termed HTS-1, was established. In the present investigation, the 5'-upstream region of ovine IFNtau (oIFNtau) gene was analysed using this cell line, which would provide a more suitable system for studies of the ovine trophoblast specific gene than human choriocarcinoma cells. Variously modified 5'-upstream sequences of the oIFNtau gene fused to a luciferase reporter gene were transiently transfected into HTS-1 cells, and human JEG-3 cells were used as a control. These results and co-transfection with expression vectors revealed that Ets-2 binding site in the promoter region was important in HTS-1, whereas AP-1 that binds to the enhancer region was a major activator in JEG-3. By electrophoretic mobility shift assay, a nuclear protein from HTS-1 cells was confirmed to bind specifically to the Ets-2 site of oIFNtau promoter region. Differences in amounts of AP-1 and Ets-2 protein were demonstrated in nuclear extracts from HTS-1, JEG-3 and ovine conceptuses. Substantial differences on oIFNtau gene transcriptions found between caprine HTS-1 and human JEG-3 cells suggest that this cell line could be valuable in the elucidation of a molecular mechanism(s) by which oIFNtau gene expression is regulated in a cell specific manner.

Lack of an association between plasma follicle-stimulating hormone concentrations and ovarian weight in prepubertal gilts1

Selection for increased number of corpora lutea in gilts is associated with increased plasma FSH concentrations during pubertal development. In the current study, 270 gilts from a control (CO) line and a line selected for increased ovulation rate (OR) were unilaterally ovariectomized at 85 d of age, and this ovarian weight was related to FSH concentrations at 65, 75, and 85 d of age. Gilts were produced during two farrowing seasons, spring and fall, and the age at first estrus was monitored from 160 to 250 d. Plasma FSH was greater in OR than in CO gilts at 65 (P < 0.01) and 75 d (difference in spring greater than in fall, P < 0.01), but FSH at these ages was not correlated with ovarian weight at 85 d. At 85 d, FSH did not differ in gilts of these lines; however, FSH was negatively correlated (r = -0.27, P < 0.01) with ovarian weight. The proportion of gilts detected in estrus was less for spring-born CO gilts than for spring-born OR or for fall-born CO and OR gilts (78 vs. 92%, season x line, P < 0.02). The age at first estrus was similar in the two lines but was earlier (P < 0.01) for spring-born than for fall-born gilts (194 vs. 204 d). Concentrations of FSH at each of the ages examined were not correlated with the age at first estrus. These observations support the conclusion that selection for a greater number of corpora lutea produces a correlated increase in plasma FSH during early pubertal development. This increase in FSH most likely reflects differences in FSH synthesis and release and not differences in the stage of pubertal development.

Effect of progesterone, mifepristone, and estrogen treatment during early pregnancy on conceptus development and uterine capacity in Swine

A series of experiments was performed to investigate the influence of progesterone at Days 2 and 3 of pregnancy on conceptus development and uterine capacity. In experiment 1, unilaterally hysterectomized-ovariectomized (UHO) white crossbred gilts were given no treatment, estradiol valerate (5 mg given on Days 11 and 12), or progesterone (200 mg/day on Days 2 and 3 after mating). On Day 105 of pregnancy, each fetus and its associated placenta were weighed, and the number of live and dead fetuses was recorded for each litter. Early progesterone treatment reduced (P < 0.05) litter size (a measure of uterine capacity in UHO gilts). In experiment 2, intact white crossbred gilts were mated, given no treatment or progesterone treatment on Days 2 and 3 of pregnancy, and farrowed. Progesterone treatment decreased (P < 0.05) pregnancy rates. In pregnant gilts, progesterone had no effect on the number of live or stillborn piglets at birth, and gestation length was decreased (P < 0.05). Progesterone treatment did not affect the number of large or small piglets. In experiment 3, intact gilts were mated at estrus and then received 1). no treatment or treatment with 2). 100 mg, 3). 200 mg, or 4). 400 mg mifepristone (also known as RU486) on Day 2 of pregnancy. On Day 11 of pregnancy, both uterine horns were flushed, the number and diameter of each conceptus was recorded, and the flushed material was assayed for total protein and acid phosphatase. The 400 mg mifepristone treatment decreased conceptus diameter (P < 0.05) and total protein (P = 0.06) in the uterine flushings. In experiment 4, UHO gilts were mated at estrus, injected with either corn oil (control) or mifepristone (400 mg) on Day 2 of pregnancy, and killed on Day 105 of pregnancy, and the number and weight of live fetuses and placentas was recorded. In contrast to the effect of progesterone treatment, mifepristone decreased uterine capacity by decreasing the number of small conceptuses. These data suggest that progesterone concentrations on Days 2 and 3 of pregnancy in swine influence the rate of conceptus development during early pregnancy and uterine capacity during later pregnancy.

11beta-hydroxysteroid dehydrogenase and glucocorticoid receptor messenger RNA expression in porcine placentae: effects of stage of gestation, breed, and uterine environment

Glucocorticoids are known to influence many aspects of prenatal development. Three important regulators of glucocorticoid actions at the cellular level are the enzymes 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD-1), 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD-2), and glucocorticoid receptors (GR). The present study was conducted to determine the presence of these regulators in porcine placentae during early gestation (Days 24-40; term = 114 days) and to examine the influence of breed and uterine environment. Three pig models differing in uterine environment as reflected by embryonic survival from Days 24 to 40 were used: intact white cross-bred gilts (WC-INT); white cross-bred gilts that had been unilaterally hysterectomized-ovariectomized before puberty (WC-UHO); and intact Meishan gilts (ME). Porcine-specific partial cDNAs for 11betaHSD-1 and 11betaHSD-2 and a cRNA for GRalpha were developed and used to produce 32P-labeled probes for Northern blot analyses. The 11betaHSD dehydrogenase activity was measured in vitro at saturating concentrations of substrate and coenzyme. At Day 24 of gestation, 11betaHSD-2 mRNA, dehydrogenase activity, and GR mRNA were present, but 11betaHSD-1 mRNA was absent. All three mRNAs and dehydrogenase activity increased (P < 0.01) by Day 40. On Day 30, placental 11betaHSD-2 mRNA was decreased (P = 0.03) by 47% in WC-UHO versus WC-INT. Placental 11betaHSD dehydrogenase activity was 2-fold greater (P < 0.01) in ME versus WC-INT on Day 24 of gestation. These results demonstrate, to our knowledge for the first time, the presence of 11betaHSD-1, 11betaHSD-2, and GR mRNA as well as 11betaHSD dehydrogenase activity in the porcine placenta during early pregnancy. Moreover, a role for glucocorticoids in porcine embryonic development is suggested.

The effect of breed and intrauterine crowding on fetal erythropoiesis on day 35 of gestation in swine

In a previous report, it was suggested that intrauterine crowding impaired fetal erythropoiesis and that fetal erythropoiesis was accelerated in Meishan pigs during early pregnancy. Because these conclusions were based on limited numbers of observations, the present experiment was undertaken to provide a more extensive investigation of these phenomena. Intact white crossbred gilts, unilaterally hysterectomized-ovariectomized (UHO) white crossbred gilts, and intact Meishan gilts (n = 13 to 16 per group) were mated after at least one estrous cycle of normal duration (17 to 23 d). Gilts were laparotomized at d 35 of pregnancy, the uterine horns were exteriorized and opened near each fetus, and a blood sample was collected from each fetus. The uterine horn was then surgically removed, and each fetus and placenta was weighed. All fetal blood samples were measured for hematocrit, red blood cell number, and hemoglobin. Erythropoietin and the percentages of nucleated cells and reticulocytes were also measured in blood samples from the largest and smallest living fetus in each litter. Fetal hematocrits were not affected by treatment. Blood cell counts were greater (P < 0.01) in fetuses of Meishan gilts than in White crossbred intact or UHO gilts. Hemoglobin was less (P < 0.01) in fetuses of Meishan gilts than in fetuses of White crossbred intact or UHO gilts. The percentages of nucleated (immature) cells and reticulocytes were both less (P < 0.01) in fetuses of Meishan intact gilts. Erythropoietin was also lower (P < 0.01) in fetuses of Meishan gilts. As observed previously, fetal weight was correlated (r = 0.38; P < 0.01) with blood hemoglobin concentration. These results confirm that fetal erythropoiesis in Meishan gilts is accelerated compared with White crossbred gilts. These results are consistent with the hypothesis that faster blood cell development could be beneficial to fetal survival in swine.

Characterization of porcine uterine estrogen sulfotransferase

A quantitative trait locus (QTL) for uterine capacity is located on chromosome 8. Comparison of porcine and human genetic maps suggested that the estrogen sulfotransferase (STE) gene may be located near this region. The objectives of this study were to clone the full coding region for STE, compare endometrial STE gene expression between Meishan and White composite pigs during early pregnancy, and map the STE gene. We obtained a clone (1886 bp) containing the full coding region of STE by iterative screening of an expressed sequence tag library. Endometrial STE mRNA expression in White composite gilts was determined by Northern blotting on days 10, 13, and 15 of the estrous cycle; and on days 10, 13, 15, 20, 30, and 40 of pregnancy. STE mRNA expression was elevated (P < 0.01) on days 20 and 30 of pregnancy compared to other days of the cycle or pregnancy. Endometrial STE mRNA expression during early pregnancy, determined using real-time RT-PCR, was elevated (P < 0.01) on day 20 compared to day 15, decreased (P = 0.02) between days 20 and 30, and decreased further (P < 0.01) between days 30 and 40 in both Meishan and White composite pigs. Expression of STE mRNA was greater (P = 0.01) in White composite pigs compared to Meishan pigs. Using a microsatellite from an STE containing BAC genomic clone, the STE gene was mapped to 65 centimorgans on chromosome 8. Because STE mRNA expression differs between Meishan and White composite pigs, the STE gene may be a candidate for the uterine capacity QTL.

Regulation of endometrial granulocyte macrophage-colony stimulating factor (GM-CSF) in the ewe

Granulocyte macrophage-colony stimulating factor (GM-CSF) increases ovine interferon-tau (oIFNtau) secretion by ovine conceptuses, but endometrial production of GM-CSF has not been characterized. Endometrial GM-CSF expression was evaluated in ovariectomized ewes implanted with estradiol-17beta (E(2)) and/or progesterone (P(4)) for 14 days, in day 14 cyclic and day 14 pregnant ewes. Relative levels of endometrial GM-CSF mRNA were 3-fold higher in E(2)- and E(2)/P(4)-treated ewes than that of control or P(4)-treated ovariectomized ewes. Levels of endometrial GM-CSF mRNA for cyclic ewes were similar to E(2)- and E(2)/P(4)-treated ewes, but amounts of GM-CSF mRNA in pregnant ewes were 2-fold higher. GM-CSF concentrations in endometrial culture media, determined by GM-CSF bioassay, for cyclic and E(2)/P(4)-treated ovariectomized ewes were 3-fold higher than those of control, E(2)- and P(4)-treated ovariectomized ewes; however, amounts of GM-CSF in pregnant ewes were 2-fold higher. Immunoreactive GM-CSF, examined by western blot, was detected in the culture medium from E(2)/P(4)-treated ovariectomized, cyclic and pregnant ewes. Luminal and glandular epithelia and stromal regions were determined to be sites of GM-CSF expression by immunohistochemistry and in situ hybridization techniques. Data indicate that combined E(2) and P(4) treatment of ovariectomized ewes is sufficient to restore GM-CSF expression to the level found in cyclic ewes; however, GM-CSF mRNA and protein in pregnant ewes is 2-fold greater than in ovariectomized or cyclic ewes. These data suggest that the conceptus, in addition to steroids, may play a role in the regulation of endometrial production of GM-CSF.

Detection of transforming growth factor-alpha and epidermal growth factor receptor mRNA and immunohistochemical localization of their proteins in the ovine uterus during the early implantation period

Accumulated evidence suggests that growth factors of the epidermal growth factor (EGF) family play an important role in the murine implantation process. In the sheep, however, the uterine distribution of these factors and their receptor, EGF receptor (EGF-R), during implantation is not known. This study examined the presence of mRNA transcripts and immunohistochemical localization for transforming growth factor-alpha (TGF-alpha), the potent EGF-family member, and EGF-R in the ovine uterus during the early implantation period. By reverse transcriptase-polymerase chain reaction and sequencing of the products, the presence of TGF-alpha and EGF-R mRNA transcripts were detected in the endometrium on Days 14, 16 and 20 (Day 0 = day of mating). Immunohistochemical analysis revealed that the luminal and glandular epithelial cells and some stromal cells of the endometrium and the trophectoderm were positive for TGF-alpha and EGF-R on Days 14 and 15. Distinct staining for TGF-alpha was observed in the glandular epithelium of deep endometrial areas and strong immunoreactivity for EGF-R was found in the trophectoderm. On Days 16, 18 and 20, although the staining pattern for TGF-alpha was similar to that on the previous days, the immunoreactivity for EGF-R in the stromal cells increased and that in the gland decreased. A distinct immunoreactivity for EGF-R was found in the trophectoderm throughout the days examined. These results suggest that TGF-alpha expressed in the endometrium and trophectoderm may exert effects locally on these tissues during implantation in sheep. Furthermore, it is speculated that the temporal changes in the uterine EGF-R distribution may be related to the endometrial microvascular development.

Interrelationships among conceptus size, uterine protein secretion, fetal erythropoiesis, and uterine capacity

The interrelationships among d-11 conceptus size, d-105 placental weight, placental efficiency (the ability of the placenta to support fetal growth and development), fetal erythropoiesis, and uterine capacity were examined in 1/2 Meishan, 1/2 White crossbred gilts that were unilaterally ovariohysterectomized at 90 to 100 d of age. In Exp. 1, gilts were mated after at least one normal estrous cycle and then slaughtered at 105 d of gestation and number of fetuses and CL, placental weights, fetal weights, hematocrits, fetal plasma iron, and fetal plasma folate were measured. In Exp. 2, gilts were mated and plasma progesterone was measured on d 2 and 3 of gestation. On d 11, the length of the remaining uterine horn was recorded and the uterine horn was flushed with minimal essential medium. Number of CL, conceptus number, conceptus diameters, and total uterine flush retinol-binding protein (tRBP), acid phosphatase (tAP), and folate-binding protein (tFBP) were measured. Gilts were mated again and slaughtered at 105 d of pregnancy and the same traits measured in Group 1 were recorded. Plasma progesterone concentrations on d 2 and 3 were correlated with average conceptus diameter on d 11 (r = 0.60, P < 0.01, for each day). In contrast, tRBP (r = 0.49, P < 0.01), tAP (r = 0.53, P < 0.01), and tFBP (r = 0.51, P < 0.01) in uterine flushings on d 11 were only correlated with d-3 plasma progesterone concentrations. No correlations between d-11 average conceptus diameter or d-11 uterine length with d-105 uterine capacity were observed. Uterine capacity was negatively correlated with placental weight, fetal weight and fetal hematocrit (r = -0.36, P < 0.01; r = -0.44, P < 0.01; r = -0.32, P < 0.01; respectively). Hematocrits were correlated with fetal plasma iron (r = 0.50, P < 0.01) and folates (r = 0.44, P < 0.01). Hematocrit, plasma iron, and plasma folate were each correlated with residual fetal weights after adjusting for placental weight (a measure of placental efficiency), and accounted for 11% of the variation in this trait. These data suggest that conceptus diameter and uterine protein secretion on d 11 may be influenced by the onset of progesterone secretion by the CL, but do not support an influence of conceptus growth during early pregnancy on uterine capacity. These results also suggest that reducing placental and fetal weights will likely result in increased uterine capacity.

Level of dietary energy during prepubertal growth and reproductive development of gilts

Development of gilts that conceive early and continue to produce offspring is a primary objective of swine production. The objective of this study was to determine the degree of feed restriction during development required to optimize reproductive performance and efficiency in gilts. The effects that various patterns of growth had on reproductive development and performance of gilts through d 30 of gestation were investigated. At 13 wk of age and 41 kg BW, 192 white crossbred gilts were penned individually and assigned to receive 87.5%, 75%, 62.5%, and 50% of predicted ad libitum energy intake. The study was replicated in two seasons. At 25 wk of age, gilts were moved to group pens and allowed ad libitum access to feed, and estrous detection was initiated. Gilts were inseminated at first observed estrus and those recycling were remated. Post-mating gilts were fed 1.5x maintenance in stalls. Gilts that did not return to estrus 17 to 30 d after mating were slaughtered at 30 d of gestation. Reproductive tracts were collected and numbers of corpora lutea and live embryos were recorded. Feed restriction during development resulted in differences in BW and backfat thickness at the start of the breeding period and differences in feed intake during breeding. Gilts subjected to the greatest feed restriction during development consumed the greatest quantity of feed during breeding. Feed intake during breeding was associated with BW and backfat gain during breeding. The treatment group that entered breeding lightest and leanest (50% of predicted ad libitum intake) had the least number of days to first estrus, followed by the fattest, heaviest group (87.5% of predicted ad libitum intake). Treatment groups did not differ (P > 0.38) in ovulation rate or live embryo numbers. Significant relationships between quantity of GE consumed during development and variables considered important in reproductive development and performance were evident, such as BW and fatness at start of breeding and first detected estrus, and ovulation rate. Variation in dietary energy during the development period impacted many aspects of reproductive development and performance. However, coupling restricted energy intake during development with ad libitum intake during breeding negated many of the effects of feed restriction during the development period.

Increased plasma follicle-stimulating hormone concentrations in prepubertal gilts from lines selected for increased number of corpora lutea

Plasma follicle-stimulating hormone (FSH) was evaluated in gilts from two studies in which ovulation rate was increased through direct selection for number of corpora lutea (CL) to determine whether selection for ovulation rate affected FSH secretion during prepubertal development. In the first study, 76 control and 110 selected gilts of University of Nebraska gene pool lines were bled twice during prepubertal development. Plasma FSH concentrations were greater (P < 0.05) at 53 (13.5%) and 75 (21.3%) d of age in selected than in control gilts. In the second study, 254 control gilts, 261 gilts from a line selected for ovulation rate, and 256 gilts from a line selected for uterine capacity were bled at three prepubertal ages. Plasma FSH was greater (P < 0.05), relative to controls, on d 34 (> 24%), 55 (> 13%), and 85 (> 10%) in White Composite gilts selected for either increased ovulation rate or for greater uterine capacity. Unilateral ovariectomy and hysterectomy were performed at 160 d of age on random gilts in these three lines (n = 377); weights of these organs were evaluated to determine whether selection affected their development. Ovarian and uterine weights were less (P < 0.01) in the control than in the ovulation rate line. Subsequently, ovulation rate was determined during pregnancy (n > or = 130 gilts/line). Controls had fewer (P < 0.01) CL (14.6) than gilts of the ovulation rate line (17.7) but numbers similar (P > 0.10) to those of gilts of the uterine capacity line (14.7). Within each line, plasma FSH only on d 85 correlated positively with subsequent ovulation rate (P < 0.03, 0.001, and 0.08; r = 0.17, 0.30, and 0.15 for control, ovulation rate, and uterine capacity lines, respectively). Ovarian weight at 160 d of age also correlated with subsequent ovulation rate (P < 0.03 and 0.001; r = 0.23 and 0.38) in control and ovulation rate gilts but not in uterine capacity gilts (P > 0.10; r = 0.11). Gilts selected for increased number of CL, in two independent studies, had greater concentrations of FSH during prepubertal development than respective controls. The modest but significant, positive association of FSH at 85 d of age with subsequent ovulation rate provides additional support for using plasma FSH in prepubertal gilts to indirectly select for ovulation rate.

Characterization of uterine epidermal growth factor during early pregnancy in pigs

Genomic research has identified a quantitative trait locus for uterine capacity, a component trait contributing to litter size, on porcine chromosome 8. The epidermal growth factor (EGF) gene, on porcine chromosome 8, may influence uterine capacity because of its growth-promoting activities. Using reverse transcription-polymerase chain reaction (PCR) and iterative screening of a porcine reproductive tissue cDNA library, 4932 bp cDNA sequence coding for porcine EGF precursor was obtained. The predicted protein sequence of the EGF precursor contained 1214 amino acids, similar to human EGF precursor (1207 amino acids, 81% identity). Curiously, the sequence of the mature peptide was less homologous between species than other regions of EGF precursor. The presence of conserved regions outside the mature peptide may suggest that these regions are functionally important. Expression of EGF mRNA in the endometrium of White crossbred gilts (n = 3 to 5 each) was determined by Northern blotting using 20 microg of total RNA from endometrium of D 10, 13, and 15 cyclic, and D 10, 13, 15, 20, 30, and 40 of pregnant gilts. A 3342 bp probe from EGF precursor was used. The bands corresponding to EGF mRNA were quantified by densitometry and results were analyzed by ANOVA. EGF mRNA expression decreased significantly from D 13 to 15 of the cycle and pregnancy (P = 0.04), and from D 30 to 40 of pregnancy (P = 0.01). These findings show that EGF mRNA expression is temporally regulated during the cycle and early pregnancy, and this pattern of gene expression may be important during early conceptus development.

Erythropoietin mRNA expression in pig embryos

To address whether altered erythropoietin (EPO) synthesis might be involved in prenatal pig mortality, studies were conducted to measure porcine embryonic EPO mRNA expression during early gestation (days 24-40). Three pig models differing in embryonic survival from days 24-40 were investigated: intact white crossbred gilts (INT), white crossbred gilts that were unilaterally hysterectomized-ovariectomized before puberty and whose pregnant uterus constituted a crowded environment (UHO), and prolific, intact Meishan gilts (ME). A partial cDNA for porcine EPO, developed via reverse transcription and polymerase chain reaction procedures was used to generate a 32P-labeled probe for use in Northern analyses. In an initial study, embryonic liver EPO mRNA was greatest on day 24, decreased by day 30 (P<0.01), and was barely detectable by day 40. EPO mRNA expression was not influenced by pig model. Placental EPO mRNA expression was detectable in only 4 of 53 placentae examined. In a second study at day 35 of gestation, embryonic liver EPO mRNA expression was measured in the same three pig models and in two embryos of divergent weights from each gilt. Meishan embryos had lower (P<0.01) plasma immunoassayable EPO concentrations (P=0.04) and higher survival rates (87+/-2.7%) at day 35 than did white crossbred embryos (75+/-5%). Liver EPO mRNA expression did not differ among animal models, nor did plasma EPO or tissue EPO mRNA expression differ between large and small embryos. There was no apparent relationship between embryonic development, measured as embryonic and placental size, and plasma EPO concentrations or liver EPO mRNA expression. These results indicate that at the gestational ages examined, the embryonic liver is one source of plasma erythropoietin and suggest that at the ages sampled, EPO is not a limiting factor in embryonic development.

Effect of prepubertal feeding regimen on reproductive development and performance of gilts through the first pregnancy

Development of gilts that conceive early and continue to produce offspring is an objective of swine production. We investigated different patterns of growth on reproductive development and performance of gilts through the first farrowing. At 13 wk of age and 43 kg BW, 286 white crossbred gilts were penned individually and assigned to treatments: Ad lib, ad libitum intake from 13 to 25 wk of age; Control, ad libitum intake from 13 wk of age until 100 kg BW and then 90% of ad libitum intake until 25 wk of age; and Restricted, 74% of ad libitum intake from 13 wk to 25 wk of age. Feed was formulated to restrict energy intake. The study was replicated in three seasons. At 25 wk of age, gilts were moved by treatment to group pens, fed for ad libitum consumption, and estrus detection was initiated. Gilts were inseminated at first estrus, and those recycling were remated. Postmating gilts were fed 1.5x maintenance until 105 to 110 d of pregnancy. Gilts were moved either to the farrowing facility or the abattoir at 105 to 110 d of pregnancy. Those taken to the abattoir were slaughtered and number, weight, and condition of the fetuses were recorded. Gilts moved to the farrowing facility were allowed to farrow, and number, weight, and condition of the piglets were recorded. Daily feed intake during breeding was 3.4 kg/d by Restricted gilts, 2.9 by Control gilts, and 2.7 kg/d by Ad lib gilts. Increased feed intake by Restricted gilts during breeding resulted in compensatory gains that overcame the reduced reproductive performance that resulted from the reduced BW and backfat these gilts carried at the start of breeding. Days to first estrus and pregnancy were not influenced by development period treatment (P < 0.13). Percentage of Ad lib, Control, and Restricted gilts that successfully completed their pregnancies were 61, 74, and 66, respectively (P > 0.19). Total feed fed from 13 wk of age to end of the first pregnancy per gilt assigned did not differ among Ad lib (506 kg) and Control (498 kg) gilts but was less (P < 0.01) in Restricted gilts (451 kg). Number of piglets born per gilt assigned (P > 0.09) and piglets produced per kilogram of feed fed from 13 wk of age to term (P > 0.29) were 6.47 and 0.0134 in Ad lib gilts, 7.26 and 0.0150 in Control gilts, and 6.38 and 0.0149 in Restricted gilts, respectively. Moderate feed restriction, 74% of ad libitum intake, reduced feed consumed from 13 wk of age to end of the first pregnancy with no significant impact on efficiency of piglet production.

Enhancer regions of ovine interferon-tau gene that confer PMA response or cell type specific transcription

Interferon-tau (IFNtau), produced by the trophectoderm of peri-implantation conceptuses in ruminant ungulates, attenuates the uterine production of a luteolytic factor, prostaglandin F(2alpha), resulting in the maintenance of corpus luteum function. However, molecular mechanisms regulating the temporal/spatial expression of IFNtau gene are not clearly understood. The 5'-upstream region of the sheep IFNtau (oIFNtau) gene was examined for its transcriptional regulation in two different cell types; JEG3 cells supported the transactivation of oIFNtau-reporter construct, but HeLa cells did not. In a heterologous SV40 enhancer-oIFNtau promoter or oIFNtau enhancer-SV40 promoter systems, elements required for such cell specific transactivation were localized between -654 and -555 bases, the enhancer, but not the basal promoter region of the oIFNtau gene. In these combinations, high degrees of transactivation were observed in JEG3 cells and the activity was further enhanced by the addition of phorbol 12-myristate 13-acetate (PMA), while those responses were absent in HeLa cells. To identify nucleotide sequences responsible for cell specific expression, transient transfection studies with sequential point mutations in the enhancer elements were executed. Transactivation of oIFNtau enhancer-reporter constructs was primarily regulated by three regions containing AP-1 site, GATA like sequence and site(s) unidentified. In gel mobility shift assays (GMSAs), the AP-1 site located in the enhancer region was recognized by nuclear extracts from both cell types. However, one of the GMSA probes containing GATA-like sequence exhibited different DNA-protein complex patterns in JEG3 and HeLa cells. Observations, in which the same upstream sequence behaved differently due possibly to kinds of nuclear factors available in these cell lines, suggest that such a sequence may be involved in cell specific transactivation of the oIFNtau gene. Furthermore, the same enhancer sequences were also recognized by nuclear extracts from sheep trophoblasts, suggesting that the enhancer sequences between -654 and -555 bases of oIFNtau gene may be functioning in vivo.

Intravenous infusion of iron and tetrahydrofolate does not influence intrauterine uteroferrin and secreted folate-binding protein content in swine

The effect of exogenous iron and folate on reproductive performance in swine is equivocal. However, the effect of exogenous iron and folate on secretion of their respective uterine transport proteins has never been reported. Twenty gilts were infused (n = 5 per treatment) with either 1) saline, 2) alpha-tocopherol, 3) alpha-tocopherol plus iron citrate, or 4) alpha-tocopherol plus tetrahydrofolate on d 11 to 14 of pregnancy. Intravenous infusion of iron citrate and tetrahydrofolate increased (P < 0.05) plasma iron and folate, respectively, for 6 to 8 h after treatment. Treatments had no effect on uterine content of uteroferrin or secreted folate-binding protein in uterine flushings obtained on d 15 of pregnancy. These data suggest that uterine secretion of uteroferrin and secreted folate-binding protein are not influenced by plasma levels of iron and folate, respectively, and may provide an explanation for the equivocal effect of iron and folate treatment on reproductive performance in gilts.

Antibody repertoire development in fetal and neonatal piglets. II. Characterization of heavy chain complementarity-determining region 3 diversity in the developing fetus

Since the actual combinatorial diversity in the V(H) repertoire in fetal piglets represents <1% of the potential in mice and humans, we wondered whether 1) complementarity-determining region 3 (CDR3) diversity was also restricted; 2) CDR3 diversity changed with fetal age; and 3) to what extent CDR3 contributed to the preimmune VDJ repertoire. CDR3 spectratyping and sequence analyses of 213 CDR3s recovered from >30 fetal animals of different ages showed that >95% of VDJ diversity resulted from junctional diversity. Unlike sheep and cattle, somatic hypermutation does not contribute to the repertoire. These studies also revealed that 1) N region additions are as extensive in VDJ rearrangements recovered at 30 days as those in late term fetuses, suggesting that TdT is fully active at the onset of VDJ rearrangement; 2) nearly 90% of all rearrangement are in-frame until late gestation; 3) the oligoclonal CDR3 spectratype of 30-day fetal liver becomes polyclonal by 50 days, while this change occurs much later in spleen; 4) there is little evidence of individual variation in CDR3 spectratype or differences in spectratype among lymphoid tissues with the exception of the thymus; and 4) there is a tendency for usage of the most J(H) proximal D(H) segment (D(H)B) to decrease in older fetuses and for the longer D(H) segment to be trimmed to the same length as the shorter D(H) when used in CDR3. These findings suggest that in the fetal piglet, highly restricted combinatorial diversity and the lack of somatic mutation are compensated by early onset of TdT activity and other mechanisms that contribute to CDR3 junctional diversity.

Luteinizing hormone secretion as affected by hypophyseal stalk transection and estradiol-17beta in ovariectomized gilts

The objectives were to determine hypothalamic regulation of pulsatile luteinizing hormone (LH) secretion in female pigs and the biphasic feedback actions of estradiol-17beta (E(2)-17beta). In the first study, the minimum effective dosage of E(2)-17beta that would induce estrus in ovariectomized gilts was determined to be 20microg/kg body weight. In the second study, ovariectomized gilts were assigned randomly on day 0 to treatments: (a) hypophyseal stalk transection (HST), (b) cranial sham-operated control (SOC), and (c) unoperated control (UOC). On day 3, gilts from each group received a single i.m. injection of either E(2)-17beta (20microg/kg body weight) or sesame oil. Blood was collected from an indwelling jugular cannula at 15min intervals for 3h before (day -2) and after treatment (day 2) from HST, SOC and UOC gilts. On day 3, blood was collected at 2h intervals for 12h after E(2)-17beta or sesame oil injection and at 4h intervals thereafter for 108h. Pulsatile LH secretion in all gilts 2 days after ovariectomy exhibited a frequency of 0.9+/-0.06peaks/h, amplitude of 1.3+/-0.13ng/ml, baseline of 0.8+/-0.07. Serum LH concentrations from SOC and UOC gilts were similar on day 2 and profiles did not differ from those on day -2. In HST gilts pulsatile LH release was abolished and mean LH concentration decreased compared with controls (0 versus 0.9+/-0. 06peaks/h and 0.77+/-0.03 versus 1.07+/-0.07ng/ml, respectively; P<0. 05). E(2)-17beta or sesame oil did not affect serum LH concentration in HST gilts, and LH remained constant throughout 120h (0.7+/-0. 07ng/ml). In SOC and UOC control gilts, E(2)-17beta induced a 60% decrease (P<0.05) in LH concentration within 12h, and LH remained low until 48h, then increased to peak values (P<0.05) by 72h, followed by a gradual decline to 120h. Although pituitary weight decreased 31% in HST gilts compared with controls (228 versus 332mg, P<0.05), an abundance of normal basophils was evident in coronal sections of the adenohypophysis of HST comparable to that seen in control gilts. The third and fourth studies determined that hourly i. v. infusions of LHRH (2microg) and a second injection of E(2)-17beta 48h after the first had no effect on the positive feedback action of estrogen in UOC. However, in HST gilts that received LHRH hourly, the first injection of E(2)-17beta decreased (P<0.05) plasma LH concentrations while the second injection of E(2)-17beta failed to induce a positive response to estrogen. These results indicate that both pulsatile LH secretion and the biphasic feedback action of E(2)-17beta on LH secretion depend on hypothalamic regulatory mechanisms in the gilts. The isolated pituitary of HST gilts is capable of autonomous secretion of LH; E(2)-17beta will elicit direct negative feedback action on the isolated pituitary gland if the gonadotropes are supported by exogenous LHRH, but E(2)-17beta at high concentrations will not induce positive feedback in isolated pituitaries. Thus, the direct effect of E(2)-17beta on the pituitary of monkeys cannot be mimicked in pigs.

Porcine erythropoietin receptor: molecular cloning and expression in embryonic and fetal liver

The full coding sequence for porcine erythropoietin receptor (EPOR) was elucidated using reverse transcription polymerase chain reaction (PCR) (rtPCR) and 3' and 5' rapid amplification of cDNA ends (RACE) procedures. Total RNA collected from Day 30 fetal liver was used as starting material. A 1843 bp sequence was obtained from which could be inferred a 509 amino acid protein which was 79-85% identical to the amino acid sequence of erythropoietin receptor from other species. Total RNA samples collected from white crossbred intact, white crossbred UHO and Meishan gilts on Days 24, 30 and 40 of gestation were subjected to Northern blotting using porcine EPOR cDNA as probe. Results indicated that (1) a major and two minor forms of mRNA are present, (2) fetal liver mRNA concentrations for EPOR are low on Day 24 of gestation and increase dramatically by Day 30 and (3) mRNA concentrations for EPOR tended to be decreased by intrauterine crowding.

Analysis of possible silencer elements of ovine interferon-tau gene

During the peri-implantation period significant production of ovine interferon-tau (olFNtau) by the trophectoderm is detected in day 13-16 conceptuses, but its level rapidly declines thereafter. To understand molecular mechanisms by which oIFNtau gene expression is down-regulated, a variety of deletion constructs were prepared from upstream sequences of the oIFNtau gene and examined for possible silencer regions by using transient transfection into human choriocarcinoma, JEG3, cells. Two regions between -700 to -654 bases (distal region) and from -503 to -453 bases (proximal region) were found to be the possible negative regulatory regions. With probes prepared from these regions, gel mobility shift assay (GMSA) was then conducted. DNA-protein complexes were observed, but the gel shift pattern was different between nuclear extracts from days 14 (active oIFNtau production) and 20 (minute oIFNtau production) ovine trophoblasts. Day 20 nuclear extracts exhibited more band patterns than those of day 14; most notably the distal region between -692 and -668 bases exhibited the distinct band with nuclear extracts from day 20, but not from day 14 trophoblasts. In addition, the band patterns from day 20 trophoblast nuclear proteins were similar to those detected with JEG3 and HeLa cell nuclear extracts. Taken together, these observations suggest that the upstream sequences identified could serve as negative regulatory regions to which various nuclear factors bind, resulting in reduction of oIFNtau gene transcription.

Genetic differences in the frequency of the hinge variants of porcine IgA is breed dependent

The distribution of the IgA(a) and IgA(b) alleles of porcine IgA in over 160 randomly-selected animals revealed an abundance of heterozygotes but only two b/b homozygotes. Since the IgA(b) allotype is a splice site mutant lacking two-thirds of the hinge, this study tests the hypothesis that pigs with this genotype may be at a selective disadvantage while heterozygous individuals may be at some advantage. This hypothesis was tested by collecting data on 374 animals of known breed and often parentage. We show here that when breed was not considered, young animals of known parentage had genotypic frequencies identical to that expected for Mendelian alleles but that a/b heterozygotes were overrepresented in adults. However, when analyzed with regard to breed, a very strong association between breed and the frequency of the IgA(a) and IgA(b) alleles was discovered. Meishan and NIH minipigs were homozygous for IgA while heterozygotes predominated in Berkshire, Chester White, Durocs, Hampshire and Landrace. Animals homozygous for IgA(b) were best represented in the White Cross line. We show here that this very strong breed dependency of IgA allotypy in swine can produce a sample bias that can explain why only two b/b homozygotes (1.3%) were found in the 160 randomly-selected samples since the original samples came from primarily Landrace and Yorkshire animals. The expected frequency of b/b homozygotes in these breeds would be <3%. Thus, the data presented here reject the hypothesis that swine homozygous for a trait that results in loss of two-thirds of the IgA hinge, are selected against and that heterozygotes are positively selected. Rather, the study shows that IgA(a) and IgA(b) appear to be simple, breed-dependent allotypic markers.

Isolation of complementary deoxyribonucleic acids encoding putative secreted and membrane-bound folate binding proteins from endometrium of swine

Two distinct forms of endometrial folate binding protein (FBP) cDNAs were isolated using reverse transcription-polymerase chain reaction and 3' and 5' rapid amplification of cDNA ends (RACE) procedures. On the basis of the absence or presence of an intact glycophosphatidylinositol linkage site in the C terminus of the predicted amino acid sequences, the two forms appear to encode secreted and membrane-bound forms of FBP. The cDNAs for the putative secreted and membrane forms encoded 252- and 249-amino acid proteins, respectively, that were 73% identical with each other and were 66-82% identical with other known FBPs. However, the nucleotide sequences within the 5' untranslated region and from codons 224 and 223 of the secreted and membrane forms, respectively, to the 3' ends of each RNA, were divergent. The divergence in the 3' ends of the two cDNAs was exploited to determine changes in concentrations of each mRNA in the endometrium during the estrous cycle and early pregnancy. Northern blots of endometrial total RNA probed with a putative secreted FBP specific probe indicated that mRNA concentrations do not change during early pregnancy. In contrast, blots probed with a putative membrane FBP specific probe indicated that mRNA concentrations increase dramatically from Day 15 to Day 24 of pregnancy. Finally, N-terminal amino acid sequencing of FBP purified from Day 15 pregnant uterine flushings matched the secreted form of FBP mRNA. These data are consistent with a role for putative secreted and membrane-bound forms of FBPs in the transport of folate to the developing swine conceptus during early pregnancy.

Effect of prepubertal feeding regimen on reproductive development of gilts

The effect of prepubertal feed level on growth and reproductive development of gilts was investigated. At 13 wk. of age, white crossbred gilts were penned individually and assigned to the following treatments: Ad lib, ad libitum intake from 13 to 25 wk. of age (n = 64); Control, ad libitum intake from 13 wk. of age until 100 kg BW and then 90% of ad libitum intake until 25 wk. of age (n = 65); and Restricted, 74% of ad libitum intake from 13 wk. to 25 wk. of age (n = 64). Feed was formulated to primarily restrict energy intake. The study was replicated in two seasons. At 25 wk. of age, gilts were moved to group pens, approximately 16 gilts/pen, allowed ad libitum access to feed, and estrus detection was initiated. Gilts were mated at first estrus and those recycling were remated. After mating, gilts were moved to gestation stalls and fed 1.5x maintenance. At 30 d of gestation, reproductive tracts were harvested, and numbers of corpora lutea (CL) and live embryos were recorded. From 13 to 25 wk. of age, feed consumption was 258 for Ad lib, 251 for Control, and 189 kg/gilt for Restricted, and, from 13 wk. of age until 30 d of gestation, total feed consumption was 367 for Ad lib, 356 for Control, and 299 kg/gilt for Restricted gilts. Age at puberty (196 d) and pregnancy (200 d) was not affected (P>.18) by treatment. However, the rate at which gilts attained puberty (e.g., percentage pubertal at 28 d) was greatest in Ad lib (75) and least in Control (61) gilts. Number of CL and live embryos at 30 d of gestation/gilt assigned to the study was unaffected (P>.21) by treatment. Quantity of feed consumed from 13 wk. of age to 30 d of gestation per live embryo in gilts assigned to the study was 40.0 for Ad lib, 39.8 for Control, and 30.6 kg/gilt for Restricted gilts. These results indicate that moderate feed restriction of gilts during prepubertal development may increase efficiency of swine production without negative impact on reproductive performance through 30 d of gestation.

Identification of a functional transcriptional factor AP-1 site in the sheep interferon tau gene that mediates a response to PMA in JEG3 cells

To examine regulatory mechanisms of sheep interferon tau (oIFNtau) gene expression, potential enhancer/silencer elements of the oIFNtau gene were examined using a transient transfection system with oIFNtau gene-chloramphenicol acetyltransferase (oIFNtau-CAT) reporter constructs in human choriocarcinoma cells, JEG3. Experiments with 5'-deletion constructs revealed that the upstream regions from bases -654 to -607 and from bases -606 to -555 were essential for oIFNtau gene expression. In a heterologous transcriptional system in which the upstream regions of oIFNtau were inserted in front of simian virus 40 (SV40) promoter, the regions between bases -654 and -555 were determined as being the enhancer region required for oIFNtau-SV40-CAT transactivation. A subsequent study with the oIFNtau-CAT constructs lacking the upstream region between bases -542 and -124 revealed that, in addition to the further upstream region between bases -1000 and -654, the sequences from bases -543 to -452 seemed to act as silencer regions. The oIFNtau-CAT constructs with site-specific mutagenesis revealed that multiple enhancer elements existed between bases -654 and -555 of the oIFNtau gene. On the basis of nucleotide sequence analysis, there are numerous sites between bases -654 and -555 to which potential transcriptional factors, AP-1, GATA and GATA-related proteins, could bind. Furthermore, gel mobility-shift assays revealed that AP-1 or other nuclear factors could bind to these elements. In co-transfection studies, the expression of c-Jun plus c-Fos enhanced the transactivation of oIFNtau-CAT but the expression of GATA-1, GATA-2 or GATA-3 did not. Taken together, these results suggest that the upstream region between bases -654 and -555 could be considered as the enhancer region for oIFNtau gene transactivation.

Identification of quantitative trait loci affecting female reproductive traits in a multigeneration Meishan-White composite swine population

A multigeneration crossbred Meishan-White composite resource population was used to identify quantitative trait loci (QTL) for age at first estrus (AP) and the components of litter size: ovulation rate (OR; number of ova released in an estrous period) and uterine capacity (UC). The population was established by reciprocally mating Meishan (ME) and White composite (WC) pigs. Resultant F1 females were mated to either ME or WC boars to produce backcross progeny (BC) of either 3/4 WC 1/4 ME or 1/4 WC 3/4 ME. To produce the next generation (F3), 3/4 WC 1/4 ME animals were mated to 1/4 WC 3/4 ME animals yielding half-blood (1/2 WC 1/2 ME) progeny. A final generation (F4) was produced by inter se mating F3 animals. Measurements for AP and OR were recorded on 101 BC, 389 F3, and 110 F4 gilts, and UC data were from 101 BC and 110 F4 first parity litters. A genomic scan was conducted with markers (n = 157) spaced approximately 20 cM apart. All parental, F1, BC, and F4 animals but only 84 F3 animals were genotyped and included in this study. The QTL analysis fitted a QTL at 1-cM intervals throughout the genome, and QTL effects were tested using approximate genome-wide significance levels. For OR, a significant (E[false positive] < .05) QTL was detected on chromosome 8, suggestive (E[false positive] < 1.0) QTL were detected on chromosomes 3 and 10, and two additional regions were detected that may possess a QTL (E[false positive] < 2.0) on chromosomes 9 and 15. Two regions possessed suggestive evidence for QTL affecting AP on chromosomes 1 and 10, and one suggestive region on chromosome 8 was identified for UC. Further analyses of other populations of swine are necessary to determine the extent of allelic variation at the identified QTL.

Cortisol concentrations in early porcine embryos

A study was conducted to determine the presence of cortisol in body tissue of porcine embryos at days 25 and 35 of gestation. Cortisol concentrations (ng/mg DNA) were low but measurable at day 25 and increased eightfold by day 35 during a time when body weight increased 6.4-fold. At day 35, there was a highly significant positive linear regression of body weight on cortisol concentrations. The source of this embryonic cortisol is not known, but its presence suggests the opportunity for cortisol to influence porcine embryonic development at these early gestational stages.

A radioimmunoassay for porcine intrauterine folate binding protein

A RIA was developed for porcine intrauterine folate binding protein (FBP). Displacement of [125I]FBP caused by increasing dilutions of uterine flushings collected from either d-15 pregnant or nonpregnant gilts or media from culture of endometrial tissue from d-15 pregnant or nonpregnant gilts was parallel to the displacement caused by the standard curve. Addition of known amounts of purified allantoic fluid FBP to dilutions of either intrauterine flushings or endometrial culture medium were measured accurately with the RIA. To test specificity, 2-mL samples of uterine flushings collected from d-15 pregnant and nonpregnant gilts were preincubated with 10 microCi of [3H]folic acid and then chromatographed using Sephadex G-100 (Sigma Chemical Co., St. Louis, MO). The fractions were subsequently assayed for radioactivity by liquid scintillation spectrophotometry and for FBP by RIA. The [3H]folic acid and FBP peaks coincided, indicating that the RIA is specific for FBP. Uterine flushings were collected on d 10, 11, 12, 13, 14, and 15 of the cycle or pregnancy from 1) White crossbred, 2) progesterone-treated White crossbred (200 mg of progesterone at 48 and 72 h after estrus), and 3) Meishan gilts and assayed for FBP. Total FBP increased 140-fold from d 10 to 15, and the pattern of change across day did not differ between pregnant and nonpregnant gilts. Progesterone treatment increased intrauterine FBP content on d 10 and 11. No difference in FBP concentrations was detected between White crossbred and Meishan gilts. These results indicate that the RIA for FBP is valid, allowing measurement of this protein in uterine flushings and endometrial culture medium. The onset of FBP secretion by the uterus between d 10 and 15 of the cycle or pregnancy is influenced by the timing of onset of progesterone influence in a manner similar to the endometrial proteins uteroferrin and retinol binding protein. In contrast to these endometrial proteins, FBP concentrations are similar in Meishan and White crossbred gilts.

Conceptus, progesterone, and breed effects on uterine protein secretion in swine

This experiment consisted of the following treatment-breed groups: 1) White crossbred gilts, 2) White crossbred gilts treated with progesterone (200 mg/d in corn oil given on d 2 and 3 after estrus), and 3) Chinese Meishan gilts. Pregnant and nonpregnant gilts (n=3 to 6) from each treatment-breed combination were assigned to be slaughtered on d 10, 11, 12, 13, and 15. At slaughter each uterine horn was flushed with 20 mL of minimal essential medium. Uterine flushings were assayed for total protein, acid phosphatase, uteroferrin, retinol-binding protein, and oxytocin. Uterine flush total protein was increased by progesterone treatment, was unaffected by pregnancy status, and was less in Meishans. Similar patterns were found for retinol binding protein and uteroferrin, except that uteroferrin was greater in pregnant than in nonpregnant gilts. Oxytocin was greater in pregnant than in nonpregnant gilts, was not influenced by progesterone treatment, and was similar in Meishan and in White crossbred gilts. These results indicate that the conceptus does not influence secretion of either total protein or retinol binding protein during pregnancy and that the onset of secretion of these uterine proteins may be controlled by progesterone. The presence of the conceptus is associated with increased uteroferrin and oxytocin production. The decreased secretion of uterine proteins in Meishan gilts may partially explain the slower embryonic development that has been reported for this breed.

Co-expression of transforming growth factor beta and interferon tau during peri-implantation period in the ewe

The transforming growth factor beta (TGFbeta) family is known to control cell migration, growth, differentiation, function and regulation of extracellular matrix, all of which are required for the process of implantation. Expression of TGFbeta by the conceptus and endometrium was studied during the period of implantation in the ewe. A total of thirty-four ewes were hysterectomized on day 12, 14, 16, 18 or 20 of pregnancy (day 0 = day of estrus). Conceptus (200 mg wet weight) and endometrial (300 mg wet weight) tissues were cultured in vitro in 7 and 10 ml Eagle's minimal essential medium, respectively. The culture media were subjected to a bioassay to determine concentrations of TGFbeta. Conceptus culture media (CCM) were also analyzed for contents of ovine interferon-tau (oIFNr), low molecular weight acidic protein, produced by the trophectoderm between days 8 and 21 of pregnancy. Whole uteri including conceptus(es) and conceptuses (day 16) only were fixed and subjected to immunohistochemical and in situ hybridization studies. Levels of oIFNr produced by conceptuses were the highest on day 16 at 4.4 microg/ml. Concentrations of TGFbeta in day 12, 14, 16, 18 and 20 CCM were 38+/-19, 102+/-56, 862+/-152, 728+/-191 and 336+/-106 pg/ml, respectively, and approximately 90% of TGFbeta activity in CCM was due to TGFbeta1 whereas less than 10% was due to TGFbeta3 based on neutralization with TGFbeta subtype-specific antibodies. Immunohistochemical studies revealed that day 16 conceptuses displayed major staining for TGFbeta1, no beta2 staining and minor staining for beta3. In situ hybridization studies also revealed that day 16 trophectoderm possessed most TGFbeta1 mRNA while day 14 trophectoderm and day 20 chorion/amnion displayed weaker staining for TGFbeta1 mRNA. TGFbeta in day 12, 14, 16, 18 and day 20 endometrial culture media was 156+/-37, 129+/-33, 49+/-22, 62+/-23 and 179+/-40 pg/ml, respectively, and approximately 65% and 35% of the activities were due to TGFbeta1 and beta2, respectively. These results indicate that TGFbeta production by the conceptus coincides with the time when oIFNtau production starts to decline. These observations support the postulate that TGFbeta may play an important role in implantation in the ovine species.

Purification and characterization of intrauterine folate-binding proteins from swine

Folate-binding proteins (FBP) from Day 60 pseudopregnant uterine flushings and Day 60 allantoic fluid were purified by affinity chromatography on folate-Sepharose followed by G-100 Sephadex chromatography. FBP from uterine flushings had a molecular weight of 20000; the N-terminal sequence was FNWDHXGKMEPAXKRHFXXXTXLYX, which is 72% identical to bovine milk FBP beginning at amino acid 64. Allantoic fluid FBP had a molecular weight of 30000; and the N-terminal sequence ARAKTDMLNVXMDAKHHKPKPSXED, which is 68% identical to bovine milk FBP starting at amino acid 4. Scatchard analysis of purified allantoic fluid FBP using [3H]folic acid as ligand indicated a dissociation constant of 0.54 nM, and the protein was saturated at 20 nM. Antiserum to the purified allantoic fluid FBP was generated in rabbits and used for immunoblotting. Uterine flushings were collected from pregnant and nonpregnant gilts on Days 10, 11, 12, 13, and 15. Immunoblotting indicated that FBP concentrations increased in uterine flushings from both pregnant and nonpregnant gilts between Days 10 and 15. Total uterine flush specific binding of [3H]folic acid increased from 0.015 nmol on Day 10 to 2.14 nmol on Day 15. These results indicate that an FBP similar to other known FBPs is present in uterine flushings and allantoic fluid and that its level increases at about the time of blastocyst elongation and initiation of conceptus hematopoiesis. These results suggest a role for FBP in the delivery of folate to the developing conceptus.